The radiation load on the human body consists primarily of radiation coming from technical apparatus (television, x-ray machines, etc.), cosmic radiation and artificial and natural radioactivity. Lately, we have become increasingly aware of the danger of natural radioactive radiation. This acts not only at the location of deposits of uranium-containing ore and rock, but can be found also in residential and other buildings, because of the use of uranium-containing construction materials.
Natural radioactivity appears in all elements with an atomic number higher than 80. The radioactive isotopes of these elements have mostly very short half-lifes and could not be detected today--approximately 6 billion years after their formation. However, they continue to form again and again due to alpha or beta decomposition from the decomposition of the uranium isotopes 238 and 235 with a very long life, as well as of the thorium isotope 232. As a result of the longevity of the uranium isotopes, the radioactive radiation coming from uranium is very low. However, in the course of the uranium disintegration chain which finally ends with the inactive lead a new gaseous intermediate product appears, radon 222, which disintegrates again within a short time period, but not without leaving behind a number of stable radioactive products.
Radon is a colorless, tasteless and odorless radioactive gas which due to its high atomic weight collects mainly at the bottoms of rooms. Particularly basement rooms and other rooms bordering on the ground can therefore have a considerable degree of radioactive contamination. Also materials used in construction, such as clay, construction materials containing pumice, cemented stones with slag additives or granite often contain uranium emitting gaseous, radioactive radon.
Lately, public opinion has become increasingly sensitive to the dangers of radioactive contamination, due to various accidents in nuclear power plants. At the same time, there is an increased awareness of the dangers resulting from other types of radiation, such as widespread medical testing and radiation therapy, as well as the dangers of natural radioactivity. Scientific research has proven that the health-injuring effects of natural radioactivity are considerably higher than has been assumed. It has for instance been established that in certain living spaces the radioactivity level is much higher than acceptable. It has been found that the cause is the accumulation of radon in dangerous concentrations in residential and other buildings, whereby especially the building basement floors with poor ventilation and the buildings without basements, erected directly on the soil, are particularly afflicted by radon infiltrating from the surrounding soil.
For this reason, lately measures for the reduction of radon infiltration in living spaces have been proposed. However, the known measures are either effective for only a short time, e.g. intensive ventilation of these rooms, or complicated, expensive and short-lived. For instance wall hangings of plastic foil, e.g. polyvinyl chloride or polyurethane or of light metal, have been proposed. It has also been proposed to seal the rooms with polyurethane resins. However, these known steps have not proven themselves in practice, since they can not completely cover the nooks and crannies and also can not evenly and completely cover the curves or corners. Besides, these known web-like coverings made of plastic or light metal, unlike the usual wall coverings, cannot be covered with tiles or plaster, or they tend to disintegrate or lose adhesion due to their incompatibility with the usual construction substrates and because of humidity.
It is, therefore, an object of the invention to avoid the drawbacks of the known methods for the reduction of the radon load in closed spaces and particularly to provide a long-term and highly efficient method which makes it possible to prevent the infiltration of radon gas from the ground and the emission of this gas from construction materials into the rooms to be protected.
It is a further object of the invention to provide a method which makes it possible to apply to external construction parts (walls, floors and ceilings) a substance for the protection against radon infiltration, with simple and traditional means.
Yet another object of the invention is to provide a substance for blocking incursion of radon and which can be applied to all traditional building materials, such as stone, concrete, gypsum, etc., but which remains stable under the action of humidity and chemicals.
Finally, another object of the invention is to provide a substance which, applied according to the method of the invention, lends itself to the application of decorative surfaces or of functional layers.